91av

UNTIL recently, it was heretical for a biologist to argue that animals have a mental life. Because animals can’t tell us what they are feeling, most scientists thought it safest to assume that they don’t feel much at all, or that their behaviours derive from simple instinct or learning. Emotions, empathy and intelligence were considered exclusively human traits – they were what defined us as human.

Frans de Waal, who has been studying the behaviour of primates for more than four decades, has always opposed this view, which is still prevalent in some circles. For him, there has never been any question that animals experience the same emotions as humans.

“Why did we go out of our way to deny or deride something so obvious?” he asks in his latest book, Mama’s Last Hug, written before he retires this year. “Considering how much animals act like us, share our physiological reactions, have the same facial expressions, and possess the same sort of brains, wouldn’t it be strange indeed if their internal experiences were radically different?”

The title of de Waal’s book refers to a final reunion between Mama, a dying 58-year-old chimpanzee, and Jan van Hooff, a 79-year-old biologist who had known her for 40 years (the has been watched more than 10 million times since it was posted in 2016).

When she realises who he is, Mama rouses herself from her lethargy, grins expansively and embraces van Hooff. It is hard not to interpret her reaction as sheer joy, and de Waal believes that we are right to do so. “Instead of tiptoeing around [the emotions], it’s time for us to squarely face the degree to which all animals are driven by them,” he writes.

In 1872, Charles Darwin made a similar point in The Expression of the Emotions in Man and Animals. Despite its initial success, this book was overlooked by scientists for more than a century. Discomforted by Darwin’s references to affectionate cats, disappointed chimps and happy cows, they championed human exceptionalism, the idea that we are a cognitively superior species. As de Waal writes inMama’s Last Hug, this has not only corrupted our understanding of animals, but also of ourselves.

“He envisages a science of animal feelings. For now, it is enough that we take seriously what is visible”

There is nothing sentimental about de Waal’s position, and he draws the line at conjecturing about how animals feel – how they subjectively experience their emotions. “I’m all for assuming that species related to us have related feelings, but we should not overlook the leap of faith that it asks us to take.” All the things he has learned about animals have come from observation. He is a brilliant observer, and is often amazed by what he sees.

He was among the first to understand the importance of reconciliation among apes after watching two rival male chimps make up after a fight by grooming each other’s behinds. Hours spent scrutinising the submissive grins of monkeys and the playful grunts of chimps helped him and his colleagues unpick the separate evolutionary origins of smiling and laughter. And his analysis of thousands of facial expressions among the chimp colony at Yerkes National Primate Research Center in Atlanta, Georgia, where he works, revealed how quickly the animals shift from one emotional state to another.

If these traits sound familiar, that is the point. Animal emotions are human emotions, even if some of them are more developed in us. It would be surprising if any of our emotions were uniquely human, given that they arise from changes in the body and, as de Waal reminds us, all mammalian bodies are essentially the same.

So what does this emotional continuum tell us about ourselves? Great ape species vary considerably in their behaviours, so take your pick. Primatologist Richard Wrangham has argued that the violence of chimp societies implies warfare is innate to humans. But the stand-out feature of our species is arguably our ability to cooperate and keep the peace, which makes us more like bonobos. Nevertheless, we are not a “higher order” version of either species: it is more complex than that because we share a common ancestor, and much more besides.

Despite what de Waal calls the “anthropo-denial” of people such as neuroscientist Joseph LeDoux, who prefers science to avoid any allusion to animal emotions (despite having spent many hours studying fear in rats), he is optimistic that attitudes have largely shifted. For him, the study of the emotions is a new frontier in the science of animal behaviour.

De Waal even envisages a new science of animal feelings: the study of animals’ private experiences. But not yet. For the moment, it is enough that we take seriously what is visible on the outside.